The present invention relates to aqueous tackifiers, and methods of controlling particulates in subterranean formations using aqueous tackifiers.
Hydrocarbon-producing wells are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a viscous fracturing fluid, which also functions as a carrier fluid, is pumped into a producing zone at a rate and pressure such that the subterranean formation breaks down and one or more fractures are formed in the zone. Typically, particulate solids, such as graded sand, suspended in a portion of the fracturing fluid are then deposited in the fractures when the fracturing fluid is converted to a thin fluid to be returned to the surface. These particulate solids, or “proppant particulates,” serve to prevent the fractures from fully closing so that conductive channels are formed through which produced hydrocarbons can flow.
One hydraulic fracturing treatment particularly useful in low closure stress conditions typically observed in shallow depth reservoirs under tectonic extension is water fracturing. In water fracturing, the fracturing fluid contains a very low or zero proppant particulates concentration. Rather than relying on proppant particulates to prop open the fractures, the process instead relies on the natural conductivity created by the formation's tendency to self-prop to prevent the fractures from closing. Coal bed methane reservoirs are an example of a reservoir well-suited for proppant particulates-free water fracturing.
Unfortunately, production enhancement and open hole completions can be negatively impacted in labile formations, such as coal beds, organic rich shales, clay or organic rich clastics, and highly fractured brittle rocks. In these formations, mechanical forces or natural in-situ stress anisotropy can result in the geologic process known as spalling, where stress-related changes in the face of formation cause fine particulates, or “fines,” to “flake off” or break lose from the formation. These fines can clog the interstitial spaces of proppant packs or self-propped fractures and reduce the conductivities of the fracture, limiting the production potential of the well. Furthermore, the loose fines may also erode or cause significant wear to the production equipment used in the recovery process, and often must be separated from the produced fluids, adding further expense to the processing.
Previous attempts at controlling or mitigating the effect of loose fines have included tackification, flocculation, and agglomeration. Through these processes, the loose fines that are generated during fracturing are prevented from hindering flow as the particles migrate through the created fractures. However, most existing solutions do not address the concept of pre-stabilization of the formation before it is placed on production. Furthermore, existing solutions also typically lack the ability to remedially treat the fractures to stabilize or control the fines, and many do not offer the ability to the control the activation of the treatment fluid (e.g., the treatment fluids may not be introduced into the fracture and then activated to control or mitigate the effect of the loose fines).